1. Field of the Invention
The present invention relates to a capacitive touch sensing device and scanning method thereof.
2. Description of Related Art
Recently, the touch sensing devices that use capacitive technology have become more popular in different electronic devices. As a result, users now can input information to different devices using multiple touch input.
Please refer to FIG. 1, wherein a circuit block schematic view of a traditional capacitive touch sensing device is shown. As depicted, the capacitive touch sensing device 9 includes an electrode matrix 90, a first multiplexer 91, a driving circuit 92, a second multiplexer 93, an integrator 94, and an analog-to-digital converter 95. The electrode matrix 90 comprises a plurality of driving lines LD and a plurality of sensing lines LS; each driving line LD crosses each sensing line LS to form a coupling node 901. In addition, each coupling node 901 would induce an equivalent capacitor CE according to rules of electrical specification.
The first multiplexer 91 switches different channels in sequence for transmitting a pulse signal outputted from the driving circuit 92 to each driving line LD in turn. The second multiplexer 93 switches to receive a charge voltage induced by each sensing line LS in sequence. In other words, through the operation of the first multiplexer 91 and the second multiplexer 93, the pulse signal would make the equivalent capacitor CE induced by each coupling node 901 to be charged and discharged in turn. The integrator 94 connects to the second multiplexer 93, and stores the voltage of each equivalent capacitor CE to an integrating capacitor CI through an integrating element A1. The analog-to-digital converter 95 connects to the integrator 94, and performs an analog-to digital conversion.
The capacitive touch sensing device 9 would perform an initial process and a touch sensing process in design. In the initial process, the capacitive touch sensing device 9 would store the potential signal of equivalent capacitor CE induced by each coupling node 901 to be a base potential value individually. After that, in the touch sensing process, the capacitive touch sensing device 9 would compare the present potential signal of equivalent capacitor CE induced by each coupling node 901, with the correspondingly base potential value stored in the initial process. Thus, if any one of the coupling nodes 901 has been touched, the present potential signal of equivalent capacitor CE induced by the touched coupling node 901, would be lower than the corresponding base potential value. Therefore, the traditional capacitive touch sensing device 9 decides the coordinate position of the touched coupling node 901 by determining whether the potential signal of each equivalent capacitor CE is changed or not. However, the traditional technology can only scan and sense one coupling node at a time. If the size of the capacitive touch panel gets larger, or the requirement of the touching accuracy gets higher, the driving lines and the sensing lines would be increased, and the amount of the coupling nodes would also be increased. Accordingly, the capacitive touch sensing device would require more time to scan and sense all coupling nodes, and sensing efficiency would be reduced, and as a result, application requirement could not be met.